1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
|
/*
* Copyright © 2013 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include "brw_cfg.h"
using namespace brw;
/** @file brw_predicated_break.cpp
*
* Loops are often structured as
*
* loop:
* CMP.f0
* (+f0) IF
* BREAK
* ENDIF
* ...
* WHILE loop
*
* This peephole pass removes the IF and ENDIF instructions and predicates the
* BREAK, dropping two instructions from the loop body.
*
* If the loop was a DO { ... } WHILE loop, it looks like
*
* loop:
* ...
* CMP.f0
* (+f0) IF
* BREAK
* ENDIF
* WHILE loop
*
* and we can remove the BREAK instruction and predicate the WHILE.
*/
bool
opt_predicated_break(backend_shader *s)
{
bool progress = false;
foreach_block (block, s->cfg) {
if (block->start_ip != block->end_ip)
continue;
/* BREAK and CONTINUE instructions, by definition, can only be found at
* the ends of basic blocks.
*/
backend_instruction *jump_inst = block->end();
if (jump_inst->opcode != BRW_OPCODE_BREAK &&
jump_inst->opcode != BRW_OPCODE_CONTINUE)
continue;
backend_instruction *if_inst = block->prev()->end();
if (if_inst->opcode != BRW_OPCODE_IF)
continue;
backend_instruction *endif_inst = block->next()->start();
if (endif_inst->opcode != BRW_OPCODE_ENDIF)
continue;
bblock_t *jump_block = block;
bblock_t *if_block = jump_block->prev();
bblock_t *endif_block = jump_block->next();
jump_inst->predicate = if_inst->predicate;
jump_inst->predicate_inverse = if_inst->predicate_inverse;
bblock_t *earlier_block = if_block;
if (if_block->start_ip == if_block->end_ip) {
earlier_block = if_block->prev();
}
if_inst->remove(if_block);
bblock_t *later_block = endif_block;
if (endif_block->start_ip == endif_block->end_ip) {
later_block = endif_block->next();
}
endif_inst->remove(endif_block);
if (!earlier_block->ends_with_control_flow()) {
earlier_block->children.make_empty();
earlier_block->add_successor(s->cfg->mem_ctx, jump_block);
}
if (!later_block->starts_with_control_flow()) {
later_block->parents.make_empty();
}
jump_block->add_successor(s->cfg->mem_ctx, later_block);
if (earlier_block->can_combine_with(jump_block)) {
earlier_block->combine_with(jump_block);
block = earlier_block;
}
/* Now look at the first instruction of the block following the BREAK. If
* it's a WHILE, we can delete the break, predicate the WHILE, and join
* the two basic blocks.
*/
bblock_t *while_block = earlier_block->next();
backend_instruction *while_inst = while_block->start();
if (jump_inst->opcode == BRW_OPCODE_BREAK &&
while_inst->opcode == BRW_OPCODE_WHILE &&
while_inst->predicate == BRW_PREDICATE_NONE) {
jump_inst->remove(earlier_block);
while_inst->predicate = jump_inst->predicate;
while_inst->predicate_inverse = !jump_inst->predicate_inverse;
earlier_block->children.make_empty();
earlier_block->add_successor(s->cfg->mem_ctx, while_block);
assert(earlier_block->can_combine_with(while_block));
earlier_block->combine_with(while_block);
earlier_block->next()->parents.make_empty();
earlier_block->add_successor(s->cfg->mem_ctx, earlier_block->next());
}
progress = true;
}
if (progress)
s->invalidate_live_intervals();
return progress;
}
|
